Investigation of Popout Defects on Reinforced Concrete Sports Court Slabs in Coastal Area

This study investigates the causes of popout and blister defects on newly constructed outdoor reinforced concrete sports court slabs in tropical coastal environments. Field surveys, core sampling, compressive strength testing, Ultrasonic Pulse Velocity (UPV), rebound hammer tests, as well as SEM-EDS and XRD analyses were conducted to evaluate concrete’s physical, chemical, and microstructural properties Results indicate non- uniform coarse aggregate quality, including red-colored stones with high free lime (CaO) content, contributing to chemical instability and local expansion. Elevated Ca/Si ratios and sulfur contents exceeding 0.8% by mass suggest potential for delayed ettringite formation (DEF) and sulfate attack. XRD analysis revealed extensive calcium carbonate (CaCO₃) formation, indicative of carbonation-induced porosity increase. Furthermore, post-coating maintenance using dilute hydrochloric acid (HCl) is suspected to have weakened the surface layer and enhanced moisture ingress, promoting popout and blister formation. This research provides field-based evidence linking aggregate composition, chemical reactivity, and maintenance practices to surface deterioration, highlighting the importance of proper aggregate selection, mix design optimization, sulfate control, and avoidance of aggressive acid cleaning for durable concrete sports surfaces.